1. Walton, the LHC and the Higgs boson Cormac O’Raifeartaigh (WIT) Albert Einstein Ernest Walton

2. Overview I. LHC What, why, how II. A brief history of particles From Walton to the Standard Model III. LHC Expectations The Higgs boson Beyond the Standard Model Particle cosmology

3. The Large Hadron Collider (CERN) N o black holes High-energy proton beams Head-on collision Huge energy density Create short-lived particles E = mc 2 Detection and measurement

4. Why Explore fundamental structure of matter Investigate inter-relation of forces that hold matter together T = 10 19 K t = 1x10 -12 s V = football Study conditions of early universe Test cosmological theory Mystery of dark matter Mystery of antimatter Highest energy density since BB

5. Cosmology E = kT → T =

6. How E = 14 TeV (2.2 µJ) λ = hc/E = 1 x 10 -19 m Ultra high vacuum Low temp: 1.6 K LEP tunnel: 27 km Superconducting magnets 600 M collisions/sec (1.3 kW)

7. Particle detectors 4 main detectors CMS multi-purpose ATLAS multi-purpose ALICE quark-gluon plasma LHC-b antimatter decay

8. Particle detectors Tracking device measures momentum of charged particle Calorimeter measures energy of particle by absorption Identification detector measures velocity of particle by Cherenkov radiation

9. recycling 9 accelerators velocity increase? K.E = 1/2mv 2

10. II Particle physics (1930s) electron (1895) proton (1909) nuclear atom (1911) Rutherford Backscattering what holds electrons in place? what holds nucleus together? what causes radioactivity? Periodic Table: protons (1918) neutron (1932)

11. Four forces of nature Force of gravity Holds cosmos together Long range Electromagnetic force Holds atoms together Strong nuclear force: holds nucleus together Weak nuclear force: Beta decay The atom

12. Strong force strong force >> em charge indep (p +, n) short range Heisenberg Uncertainty massive particle 3 charge states Yukawa pion (π) Yukawa

13. Walton: accelerator physics Cockcroft and Walton: linear accelerator voltage multiplier: 0.5 MV →0.5 MeV Protons used to split the nucleus (1932) Nobel prize (1956) 1 H 1 + 3 Li 6.9 → 2 He 4 + 2 He 4 Verified mass-energy (E= mc 2 ) Verified quantum tunnelling Cavendish lab, Cambridge

14. Ernest Walton (1903-95) Born in Dungarvan Early years Limerick, Monagahan, Tyrone Methodist College, Belfast Trinity College Dublin (1922) Cavendish Lab, Cambridge (1928) Split the nucleus (1932) Trinity College Dublin (1934) Erasmus Smith Professor (1934-88)

15. New particles (1950s) Cosmic rays Particle accelerators cyclotrons synchrotrons π + → μ + + ν

16. Particle Zoo (1950s, 1960s) Over 100 particles

17. Quarks (1960s) new periodic table p +, n not fundamental gauge symmetry prediction of  - SU3 → quarks new fundamental particles UP, DOWN, STRANGE Gell-Mann, Zweig Stanford experiments 1969

18. Quantum chromodynamics scattering experiments defining property = colour SF = interquark force asymptotic freedom confinement infra-red slavery The energy required to produce a separation far exceeds the pair production energy of a quark-antiquark pair,pair production energy

19. Quark generations (1970s –1990s) Six different quarks (u,d,s,c,t,b) Six leptons (e, μ, τ, υ e, υ μ, υ τ ) Gen I: all of ordinary matter Gen II, III redundant

20. Meanwhile… Gauge theory Unified field theory of e and w forces Salaam, Weinberg, Glashow Single interaction above 100 GeV Mediated by W,Z bosons Predictions Weak neutral currents (1973) W and Z gauge bosons (CERN, 1983) Rubbia and van der Meer Nobel prize 1984

21. The Standard Model (1970s) strong force = quark force (QCD) em + weak force = electroweak matter particles:fermions (spin ½) (quarks and leptons) force carriers:bosons (integer spin) Prediction: W +-,Z 0 boson Detected: CERN, 1983

22. Standard Model: 1980s correct masses but Higgs boson outstanding key particle: too heavy?

23. III LHC expectations (SM) Higgs boson Determines mass of other particles 120-180 GeV Set by mass of top quark, Z boson Search…surprise?

24. Main production mechanisms of the Higgs at the LHC Ref: A. Djouadi, hep-ph/0503172

25. Decay channels depend on the Higgs mass: Ref: A. Djouadi, hep-ph/0503172

26. Ref: hep-ph/0208209 A summary plot:

27. Expectations II: supersymmetry Unified field theory Grand unified theory (GUT): 3 forces Theory of everything (TOE): 4 forces Supersymmetry improves GUT (circumvents no-go theorems) symmetry of fermions and bosons gravitons: makes TOE possible Phenomenology Supersymmetric particles? Not observed: broken symmetry

28. Expectations III: cosmology ? 1. Finish SM (Higgs) ? 2. Beyond the SM (SUSY) 3. Missing antimatter? LHCb 4. Nature of dark matter? neutralinos? High E = photo of early U

29. Particle cosmology

30. LHCb Tangential to ring B-meson collection Decay of b quark, antiquark CP violation (UCD group) Where is antimatter? Asymmetry in M/AM decay CP violation Quantum loops

31. Summary Higgs boson Close chapter on SM Supersymmetric particles Open chapter on unification Cosmology Missing antimatter Nature of Dark Matter New particles/dimensions Revise theory

32. Epilogue: CERN and Ireland World leader 20 member states 10 associate states 80 nations, 500 univ. Ireland not a member No particle physics in Ireland European Organization for Nuclear Research